The combined effects of global warming and pollution on development and biomineralization of sea urchins

Background – Global warming represents major threat for marine organisms already facing chemical contamination in coastal areas. Here I report the combined effects of thermal stress and exposure to three different pollutants of the marine environment (gadolinium, vanadium and phthalates) on embryos of two common Mediterranean sea urchin species with predicted opposite responses to warming, the temperate Paracentrotus lividus and the sub-tropical Arbacia lixula. Methods - Embryos were exposed to several treatments of three temperatures (18°C, 21°C, 24°C) and different concentrations of the three pollutants (from environmentally relevant to cytotoxic). The single and combined effects to thermal stress and pollutants were tested at three functional levels: i) exposure–response relationships, ii) morphological, iii) biochemical/cellular. Results - With respect to developmental progression, elevated temperatures at near-future projections accelerated development while extreme warming at present-day marine heatwave conditions breached the thermotolerance threshold of both species. We found a fascinating double side effect of increased temperature combined to pollution: a mild temperature increase reduced the negative effects of pollutants on development with a lower percentage of abnormality and improved skeleton growth, while combined heatwave conditions and pollution resulted in a lower proportion of embryos reaching the advanced larval stages. Conclusion - Our data highlight the need for a better understanding of the interactions between the multiple stressors faced by marine species in coastal environments. Project funded by the European Union – NextGenerationEU under the National Recovery and Resilience Plan (NRRP), Mission 4 Component 2, Project NBFC CUP B73C22000790001